Method of manufacturing electric heaters



(No Model,)

H. G. ONEILL. METHOD OF MANUFACTURING ELECTRIC HEATERS. No. 498,078.

Patented May 23, 1 893.

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UNITED STATES PATENT OFFICE.

HENRY G. ONEILL, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE STAND- ARDELECTRIC HEAT, LIGHT AND POIVER COMPANY, OF MAINE.

METHOD OF MANUFACTURING ELECTRIC HEATERS.

SPECIFICATION forming part of Letters Patent No. 498.078, dated May 23,1893.

Application filed August 20, 1892: Serial No. 443,610. (No model.)

To all whom it may concern.-

Be it known that I, HENRY G. ONEILL, a subject of the Queen of GreatBritain, and a resident of Boston, in the county of Suffolk and State ofMassachusetts, have invented certain new and useful Improvements inMethods of Manufacturing Electrical Heaters; and I do declare thefollowing to be a full, clear, and exact description of the invention,

to such as will enable others skilled in the art to which it appertainsto make and use the same, reference beinghadtotheaccompanyingdrawings,and to letters of reference marked thereon, which form a part of thisspecification.

Figure 1 is a bottom plan view of the upper section of the heater body,before baking and carbonizing and before covering the resistanceconductors with cement. Fig. 2 is a plan view of the lower section ofthe heater body, with the conductor shown in dotted lines. Fig. 3 is atransverse vertical section through the completed body. Fig. 4 is amodified form of the filament. Fig. 5 is a partial plan view of a heaterbody provided with the modified form of filamentillustrated in Fig.

This invention has relation to the production of apparatus, wherein theenergy of electricity is designed to be converted into heat, and itsobject is to provide a practical mode or method of manufacturingelectric heaters with an interior carbon filament of considerable lengthbut extremely small cross-section, without failure of the continuity ofsaid filament. It is designed by this invention therefore to secure, inthe carbon filament, positive continuity, necessary to conductiomwhilenevertheless its length may be considerable, and its sectional area ofextremely limited character, a result involving in any ordinary 4o modeof manufacture, on account of the fragile character of an extremely thincarbon filament, difficulties of attainment, which may be regarded, aspractically insuperable. Important features are therefore it is believed5 presented, referring not alone to the great advantage in such a heaterof the thin or fila mentous high resistance conductor in the action ofconversion, but also, to the obvious practicability and economy in themode of manufacture.

In carrying out this ipvention I prefer to make the body of the heaterof silicate of magnesia, I or fire clay, although analogous substances,which are conductors of heat and at the same time electrical insulators,may be employed. The material is designed to be reduced to powderedform, and is then mixed with any suitable non-conducting cement, such asmay be composed of the silicate of soda mingled with the powderedsubstance of which the body is made and sufiicient water to form aplastic mass. This is designed to be pressed in the desired form, whichmay be either plain or ornamental, fiat or curved, or it may be in theshape of a hollow vessel for 55 cooking purposes, or of a heatinginstrument. hen plain or flat, it may be made in sections, which mayhave their inner faces formed with slight grooves or depressions, as ata, to receive carbonizable material Z).

The carbonizable material may consist of a filament of silk or flax,cotton thread, an extremely thin strip of straw, bamboo, cane, or othersuitable substance, which when the mass is baked, will be carbonized bythe heat to which it is subjected. The filament or strip is laid in thegroove of the plate running back and forth or cross-wise in a continuousbut zig-zag manner, and at its ends metallic terminals o are attachedand the whole covered in with powdered material of the same character asthat composing the heater body, and hermetically sealed, pressure beingemployed to insure a'compact and solid condition. The plate or bodyprovided with the carbonizablc material is then thoroughly dried andafterward placed in a furnace and subjected to sufficient heat tocarbonize the filament or strip, and at the same time to harden or bakethe inclosing body.

For ordinary heaters for warming purposes, it is preferred to make thebody in two plain sections, whereof the grooves or depressions of onesection should extend widthwise, while those of the other extendlengthwise, so that 95 the carbonizable strips of one plate will lie ina plane parallel to that of the carbonizable strips of the othersection, but will nevertheless extend in a crossing direction asindicated in the drawings. In this manner, the I00 carbonizable materialmay be made of considerable length, that of one section being joined tothat of the other section at its end, as at d, and at all other points,separated therefrom bya layerof non-conductingcement e, which alsoserves to attach the two sections together.

Instead of using a single extendedfilament or strip of carbonizablematerial, I may wind it around a supporting core of some non-conductingsubstance, such as asbestus. The core with its covering is embedded inthe heater, and the filament carbonized. Such covered filament is laidin the plastic body in the manner hereinbefore described andhermetically sealed therein by the non-couducting cement, and theterminals being applied, the Whole is baked in a furnace, converting thecarbonizable strip or filament into a conductor of high resistance ofproper character to develop the maximum degree of heat from a givenoutlay of electrical energy.

The terminals or end connections for the carbon conductor, to which thefeed wires are to be attached, should be of some metal of sufficientlyhigh melting point to withstand the temperature necessary for thecarbonization of the interior filament, and it is preferred to usephosphor bronze or silicon bronze, although any metal having asufficiently high fusion point will answer. terminals must haveprojections extending within the body portion, and to these projectionsthe ends of the strip or filament may be made to adhere by means of somecarbonizable cement, such as thick molasses, or a composition of sugarand white of egg.

VVhil'e not absolutely essential, it is better to form perforations inseries as at f, between Thesethe lines of the filament, in order tofurnish points of egress for the gases of decomposition during theprocess of carbonization, as well as for vapor or moisture. After beingremoved from the furnace and slowly cooled, these perforations arefilled with the cement hereinbefore referred to. These perforations willalso assist in the drying of the plastic body, which should be slowlyand thoroughly effected before it is placed in the furnace, so that whensubjected to the necessary heat, it will not crack.

This heater, of whatever form, when properly baked in the furnace, willbe hard and durable, and will contain within it, a continuousfilamentous carbon conductor of minimum cross-section, such as it wouldbe impracticable to provide in any manner which contemplates themanipulation of such a carbon filament or strip, because of itsextremely fragile character.

Having described this invention, what I claim, and desire to secure byLetters Patent,

The method of forming electrical heaters, which consists in molding acarbonizable filament inside a heater body composed of plastic material,and in subsequently heating the body and filament to bake the former andcarbonize the latter, substantially as specified.

In testimony whereof I affix my signature in presence of two witnesses.

HENRY G. ONEILL.

Witnesses:

J. H. CoNoANNoN, J. W. PIOKERING.

